The present invention relates to an electrode wire EDM apparatus and more particularly to an improved fixture for such apparatus.
Electrical discharge machining (EDM) is a method for removing material from electrically conductive substrates through a process of melting or vaporization by high-frequency electrical sparks. An advantageous electrode for effecting a cutting action by EDM technology is an electrode wire which is charged as an anode or cathode with the workpiece bearing an opposite charge. In this regard, see METALS HANDBOOK, Vol. 3, 8th Ed., p. 227, American Society for Metals (1967), the disclosure of which is expressly incorporated herein by reference. Besides machining metal substrates for making, for example, dyes, an electrode wire EDM apparatus can cut virtually any electrically conductive workpiece including workpieces containing diamond, as shown in the following publications: "Machining of Diamond by High Energy-Density Sources", ADVANCED WELDING TECHNOLOGY, the Second International Symposium of the Japan Welding Society, Paper No. 2-6-(5), 25-27 August 1975; British Patent No. 1,338,140; and U.S. Pat. No. 3,239,321, the disclosures of which are expressly incorporated herein by reference.
Typical machine designs of an electrode wire EDM apparatus can be found in U.S. Pat. Nos. 4,103,137 and 4,239,952, the disclosures of which are expressly incorporated herein by reference. The workpiece to be cut by the electrode wire EDM apparatus is held fixed in position relative to the electrode wire by a fixture. The fixture is in the cutting or working zone which is traversed by the cutting electrode wire.
A compact is a polycrystalline mass of abrasive particles (e.g. diamond or cubic boron nitride) bonded together to form an integral, tough, coherent, high strength mass. A composite compact is a compact bonded to a substrate material such as cemented tungsten carbide. Representative U.S. Patents on compacts are: 3,141,746; 3,745,623 and 3,743,489. Compacts may be used as blanks for cutting tools, dressing tools and wear parts. In cutting polycrystalline diamond compacts and polycrystalline diamond composite compacts, it is commonly recommended that each compact be glued to the fixture for machining. Obviously, such procedure is cumbersome, time consuming, and labor intensive. Further, such crude procedure does not permit the cutting of multiple compacts with consistency for maintaining extremely fine tolerances (eg. 0.05 mm). The need for developing a fixture which can service a multitude of individual compacts in a single operation while maintaining consistency in defined tolerances repeatedly is needed in this art. The present invention addresses this problem and provides a unique, improved fixture.